Signal translating device



6 Sheets-Sheet 1 H (MAGNETIZWG FORCE) FIG. 2a

B (FLUX DENSITY) J. P. ECKERT, JR., ETAL SIGNAL TRANSLATING DEVICE DOUTPUT TIME INVENTORS JQHN PRESPEF! ECKERT,JR. THEODORE H. BONN BY ZA'NORNEY FIG.3

OUTPUT VOLTAGE July 9, 1963 J. P. ECKERT, JR.. ETAL 3,097,304

SIGNAL TRANSLATING DEVICE 6 Sheets-Sheet 2 Original Filed Sept. 24, 1953FIG. 5

R V W m T K N N c N w d EEO T VRB T W. W A

H NT July 9, 1963 J. P. ECKERT, JR, ETAL 3,

SIGNAL TRANSLATING DEVICE Original Filed Sept. 24, 1953 6 Sheets-Sheet 3FIG. 8 s F'IGBQ 0 POWER f E F +E' 5 CURRENT O BLDCK 1- ATA1 +E c o fSIGNAL III I I t ATA I I P 1 I I l I C 1 g A l I I Q FIG. 8b I I s o tPOWER 3 A1 C l 0 t BLOCK t ATA s 1 I SIGNAL 0 T AT A F109 F I x A L; 5 1l H 1 I P I I m 1 l I 1 c F A H F'|G.8c I l o i POWER C 1 t -5 a I +5 IBLOCJMS o 1 SIGNAL FIGQQ t SUPPLY AT 3 0 POWER I I i l SlGNAL +E I O tAT A o BLOCK I AT A +5 l O SIGNAL AT A INVENTORS JOHN PRESPER ECKERT,JR.

ATTORNEY July 9, 1963 J. P. ECKERT, JR. ETAL SIGNAL TRANSLATING DEVICEOriginal Filed Sept. 24, 1953 6 Sheets-Sheet 5 JOHN PRESPER ECKERT,JR.

FIG. I2 D4 -OUTPUT s +E D1 RI 0 POWER 1' INPUT A T .E I

F 3 o SIGNAL x t INPUT 2 I Dsi FIG.I3

L fi-OUTPUT D l 11 RL F CONSTANT 1 CURRENT SOURCE FIG. I30.

I f A :I B I CONSTANT S I L souRcE 1 R F B L T m \J l" INVENTORS A I BYTHEODORE H. BCNN ATTORNEY July 9, 1963 J. P. ECKERT, JR.. ETAL.3,097,304

SIGNAL TRANSLATING DEVICE Original Filed Sept. 24, 1953 6 Sheets-Sheet 6M OUTPUT F|G.|4

iu 1 II CONSTANT SOURCE FIG. I40.

B OUTPUT CONSTANT CURRENT L fi I SOURCE L \/v\- c INVENTORJ' I JOHNPRESPER ECKERT, JR.

1 THEODORE H. BONN A BY ATTORNEY United States Patent fiice wareOriginal application Sept. 24, 1953, Ser. No. 382,180. I)!- vided andthis application Jan. 6, I959, Ser. No. 785,263 6 Claims. (Cl. 30788)This application is a division of our copending application Serial No.382,180, filed September 24, 1953, now Patent No. 2,892,998.

The invention disclosed herein relates to pulse-type magnetic amplifiersand more particularly to such amplifiers which produce a steady output.It is well known that pulse-type magnetic amplifiers produce an outputs1gnal the duration of which is a function of the volt-seconds of thesignal or power pulse applied to the amplifier. However, often it ishighly desirable for such an amplifier to produce an output signal ofgreater duration. To this end this application discloses apparatusconnected to the load of a magnetic amplifier for stretching the outputtsignal produced thereby. Further, this application teaches that appliedsignals exceeding a predetermined volt-seconds relationship will producea standard output signal, that is, once the core comprising the magneticamplifier is caused to traverse its hysteresis loop due to the appliedsignal no further output will be observed.

As disclosed in our parent application these amplifiers may employferromagnetic materials. Such materials exhibit a hysteresis loop and inconjunction with a coil of wire displays a high impedance when operatingover the portion of the loop from minus residual flux density to plusresidual flux density and show a low impedance when traveling from plusresidual flux density towards plus saturation flux density. Use can bemade of these effects for signal translating and amplifying purposes. Away of using this etiect is to produce the desired output when and whilethe core occupies the high impedance portion of its hysteresis loop. Thepresent invention covers the output circuits of such devices using thiseifect.

It is therefore an object of this invention to provide a new magneticapparatus.

Another object of this invention is to provide a new magnetic apparatusfor limiting current pulses by taking advantage of the hysteresischaracteristics of the magnetic materials in the apparatus.

Another object of this invention is to provide a new magnetic apparatusincluding an integrating network for limiting current pulses by takingadvantage of the hysteresis characteristic of the magnetic materials inthe apparatus and the pulse stretching attributes of the integratingnetwork.

A further object of this invention is to provide a new signallingapparatus which produces an output that is constant in amplitude andduration.

Other objects and advantages of the invention will become apparent fromthe following description and the accompanying drawings in which:

FIGURE 1 is a diagram of an idealized hysteresis loop;

FIGURE 2 shows a basic circuit of a solid-state signal translatingdevice;

FIGURE 2a illustrates the operating time cycle for the embodiment ofFIGURE 2;

FIGURE 3 illustrates some representative output wave forms;

FIGURE 4 shows an input winding with a constant current input;

FIGURE 5 shows an input winding with a constant voltage input;

3,097,304 Patented July 9, 1963 FIGURE 6 illustrates some typical shapesof power pulses;

FIGURE 7 shows output wave forms produced by some of the power pulsesillustrated in FIGURE 6;

FIGURE 8 shows an input winding to be used in connection with theapplication of a constant current and the use of diodes and blockingpulses;

FIGURE 8a represents a first operating time cycle for the circuit ofFIGURE 8;

FIGURE 8b represents a second operating time cycle for the circuit ofFIGURE 8;

FIGURE 8c represents a third operating time cycle for the circuit ofFIGURE 8;

FIGURE '9 illustrates an input winding to be used in connection with theapplication of a constant voltage;

FIGURE 9a shows the form of pulses to be applied to the circuits ofFIGURE 9;

FIGURE 10 illustrates the three windings of a magnetic signaltranslating device to which D.C. power sources may be applied;

FIGURE 10a shows the pulse forms to be used in connection with thearrangement of FIGURE 10;

FIGURE 11 illustrates an arrangement in which the output is directlyconnected to the power winding;

FIGURE 11a shows a wave form which serves both as a power pulse and as ablocking pulse;

FIGURE 12 exemplifies the circuits of a single coil magnetic signaltranslating device;

FIGURES 13 and 13a illustrate a first example of an output winding witha circuit arrangement for obtaining a steady output;

FIGURES 14 and 14a show a second example of an output with a circuitarrangement for obtaining a steady output.

FIGURE 1 illustrates an idealized hysteresis loop of a material whichmay be used as the core member for the solid-state signal translatingdevices to be described. B signifies residual flux density and Bdesignates saturation flux density. The core material may be made of avariety of materials amongst which are the various types of ferrites andthe various kinds of ferromagnetic alloys, including Orthonik and 4-79Moly-Permalloy. These materials may have diilerent heat treatments togive them different properties. In addition to the wide variety ofmaterials applicable, the cores of the signal translating devices may beconstructed in a number of different geometries involving both closedand open paths. For example, cup-shaped cores, strips of material ortoroidal cores are possible.

It is to be understood that the invention is not limited to any specificgeometries of the cores nor to any specific materials therefor, and thatthe examles given are illustrative only. The only requisite is that thematerial possesses a hysteresis loop preferably approaching theidealized hysteresis loop as shown in FIGURE 1.

Before describing the signal translating devices, the terms to be usedin regard to diiferent kinds of electric pulses will be defined. Thereare clock pulses and signal pulses usually supply the power for theoperation of the therefore, selectively applied. It depends upon theinformation to be transmitted whether such pulses are present or not.The clock pulses are automatically applied and do not carry anyinformation. They may be subdivided into power pulses and blockingpulses. The power pulses usually supply the power for the operation ofthe signal translating device or, at least, open a gate to permitanother source to operate the signal translating device. The blockingpulses block the interference of the power pulse with the signal inputcircuit and/or of the signal input circuit with the power circuit.

FIGURE 2 illustrates the basic arrangement of parts of a solid-statemagnetic signal translating device. Part C is a core of ferromagneticmaterial. Winding I is the power winding, winding II is the outputwinding and winding III is the input winding. Power pulses are appliedto winding I at, for example, terminal B. The solid arrow at terminal Bindicates the direction of current of the power pulse. The solid arrowabove core C indicates the direction of flux that this current causes incore C. A typical shape of the power pulse versus time is shown in thewaveform of FIGURE 2a to the right of terminal B. This power pulsecauses a current to flow in the load resistor R in the direction shownby the solid arrow near winding II. The power pulse also causes acurrent to flow in winding III in the direction of the dotted arrowshown at terminal A. When a signal pulse is applied to terminal A of thesignal winding, a current is made to flow in the signal winding in thedirection of the solid arrow shown near terminal A. The waveform ofFIGURE 20' to the right of terminal A is a typical waveform which mightbe applied to terminal A. The vertical lines connecting the waveforms ofFIGURE 2a indicate the time relationship between the signal input pulse,which may or may not be present at terminal A, and the power pulse whichoccurs at terminal B.

The idealized BH loop of FIGURE 1 is a convenient means for describingthe method of operation of the signal translating device. First, it willbe assumed that there are no information pulses and that the power pulseis in such a direction as to drive core C from plus B to plus B In thisevent, there is a small flux change in the core, and hence an outputvoltage will be generated which, as a rule, is short in duration and, inthe case of some materials, also small in amplitude (sneak pulse).

FIGURE 3 shows representative output waveforms. Waveforms X and X arethe types which would occur in the case just discussed, namely in theabsence of an preceding the power pulse. The exact number of factors,for example, the slope of the BH loop between B and B the amplitude andwave shape of the power pulse, the value of the load resistance, thepower circuit inductance, eddy current phenomena in the core,distributed capacitances of the winding, etc.

Now, however, it will be assumed that an information pulse has occurredpreceding the power pulse. When the preceding power pulse returned to 0,it left the core in the plus B position. The information pulse causesthe material to travel from plus B to minus B in a counter-clockwisedirection around the hysteresis loop. There is a large change of flux.Any currents which tend to flow in circuit II, the load circuit, areblocked by the diode D. Therefore, the only power which must be suppliedfrom the information pulse is that power required to move the core fromplus B to minus B and the power transferred to circuit I, the powercircuit. Effective means have been found to block power transfer to thepower circuit, as will be explained hereinafter. Therefore, the onlypower consumed from the signal input circuit is the power absorbed bythe core in moving from plus B to minus B in the given time. After theperiod of time allotted to the signal pulse, the power pulse occurs andthe core now starts from inrnus B and proceeds to plus B The coreundergoes a large flux change and a large voltage is induced in windingII.

Curve Y, FIGURE 3, shows a representative output voltage versus timecurve obtained when the material is operated between minus B and plus BThe length of the output signal approximately equals the duration of thepower pulse. Note that the current induced, which is in the direction ofthe solid arrow at winding ll, FIG- URE 2, is in the direction whichwill pass through the diode D.

The power delivered to the load may be many times larger than the powerrequired of the information pulse. A net power gain is, therefore,obtainable in the signal translating device. Many factors influence theamount of power obtained. One of the most important factors, however,has to do with the extent to which the unwanted pulse, known as thesneak pulse and shown at X or X in FIGURE 3, may be tolerated in anypractical situation. Another important factor is represented by theratio of the slope on the step portion of the hysteresis loop betweenplus B and minus B to the slope of the flat portion of the hysteresisloop between plus B and plus B A material with a rectangular hysteresisloop is desirable for this signal translating device, although by nomeans completely necessary.

Thus, the fundamental method of operation of this translating device hasbeen shown. When no information pulses are applied, the material goesfrom plus B to plus B and returns to plus B only a sneak pulse as X andX in FIGURE 3 results across R When a signal pulse has been received,the material moves from plus B to minus B an output as Y in FIGURE 3results across R and the material returns to plus B Thus, the desiredoutput signal occurs when and while the material travels within thesteep middle portion of the loop where the permeability is at itsgreatest.

A signal translating device operating in the manner just described willbe designated hereinafter as an amplifier. It should be understood,however, that the use of the term amplifier is not confined to cases ofactual amplification, but extended to cover all devices which producethe desired output signal in response to the application of an inputsignal, regardless of the fact that the power, current or voltage ratiomay be greater than, equal to or less than unity. If, in contrastthereto, the desired output signal is produced in response to thenonapplication of an input signal, then the device will be called acomplementer.

It also should be realized that the device illustrated in FIGURE 2 asall the other devices described hereinafter operate as so-calledparallel magnetic amplifiers or complementers. This means that the loadcircuit or circuits are arranged in a parallel relationship to the corewhen viewed from the power source, the power being supplied, in theaverage case, by a constant current source. The desired output signalsare produced, therefore, through changes in the residual flux densitywhich, as a rule, follow the path of the hysteresis loop and keep thecore within the high permeability region, i.e., between plus and minus BIn FIGURE 2, the load on circuit 2 is shown as a resistor. However, thimight very Well be any passive or active network including resistors,capacitors, inductors, any conceivable combination thereof, computingcircuits, buffers, gates and other amplifiers.

In the waveforms illustrated in FIGURE 2a, the power pulse is shownoccurring coincident with the end of the signal pulse. The time periodt, marks the beginning of the signal pulse, 1 marks the end of thesignal pulse and the beginning of the power pulse, and t marks the endof the power pulse. Actually, t t and t mark the boundaries of theperiods allotted to the signal and power pulses and by no means indicatethe length of these pulses. The period t to t may be a relatively longtime as, for example, one minute, and the actual signal pulse may have aduration of one microsecond. This one microsecond can occur at any timeduring the one minute period allotted to the signal. The power pulse,since it always occurs, is given a period equal to its duration. Itsduration may be either greater or less than the actual duration of thesignal pulse, and it may be applied at any time after the signal pulse.Therefore, this amplifier may also serve as a memory or a delay device.In view of the fact that the power pulse is derived from a source whosewaveform can be accurately fixed, output pulses from this amplifier areof standard waveforms as determined by the power pulse source. Thisamplifier serves also, therefore, as a pulse former and pulse timingdevice.

In some instances, it may be desirable to obtain the amplifierinformation at some time which is not necessarily fixed. In this case,pulses applied to coil 1 may also be selectively controlled informationpulses. Then the amplifier functions as a delayed gate. The informationpulse applied to coil III selectively allows an output to occur whensuch output is selectively called for by an information pulse on coil I.

In FIGURE 2, the amplifier is shown with one signal input, one outputand one power winding. Actually, a signal amplifier may have many signalinput, output and power windings. Thus, it is possible for the amplifierto be operated by one of several sources and/or to operate severalloads. These sources and/or loads can have different impedance andvoltage levels and different polarities. The number of turns on thevarious windings would be adjusted to match the characteristics of theparticular circuit.

Several input circuit will now be shown to handle the various problemswhich arise in operating this type of solidstate amplifier with bothconstant current and constant voltage sources. It should be stressed, inthis connection, that the power pulse applied to coil I (the powerwinding) may, preferably, be taken from a constant current source.

A constant current source is theoretically a source of infiniteimpedance. A constant voltage source is theoretically a source of zeroimpedance. These definitions are idealized and are merely used to obtaina simplification in the analyses of circuits. From a practical point ofview, the constant current source is a source whose impedance iscompartively high with respect to the load, and a constant voltagessource is a source whose impedance is comparatively low with respect tothe load.

FIGURE 4 represents a constant current input source which can be usedwith this type of amplifier. The portion of the core C shown correspondsto coil III of FIG- URE 2. The directions of the currents, voltages, andfluxes shown are the same as those in FIGURE 2. Normally, when no signalis applied to terminal A, terminal A is at a small negative potentialsuch that the potential on the plate of diode P is zero, and the currentfrom the constant current source S flows through the diode P in serieswith A, and no current flows through coil III. In order to relax thetolerance requirements on this negative voltage, a diode Q may beinserted as shown in series with terminal A If Q is present, the smallnegative voltage may be larger and diode Q will cut off. Reverse currentwill thereby be prevented from flowing in coil III. When an input isdesired, a positive pulse is applied to terminal A; the diode P, inseries with A, cuts off; and the current which formerly flowed through Anow flows in coil III in the direction shown by the solid arrow. Thisprinciple is also applicable to the means for producing the power pulse.In this case, the actual source would be the D.C. source of constantcurrent and the source of switching pulses which cause this current toflow in coil III at the required time.

FIGURE 5 shows a constant voltage type of input in which the signalsource S is theoretically an impedanceless source. The same portion ofthe core C as in FIG- URE 4 is shown here. Z is the internal impedanceof a practical source and Z is an impedance placed in series with theinput coil III of the amplifier. The signal source S is selectivelyactuated to apply an input pulse. By placing a capacitor, shown dotted,across Z a faster change in current can be obtained.

In the previous descriptions, both the signal and the power pulse wereshown as square waves. In practice, many waveforms are possible. It isessential, however, that the signal pulse, if selectively applied, ispresent during the signal period. Whether or not this signal impulse mayextend into a. power pulse period, depends upon the characteristics ofthe other elements in the over-all circuit system within which thisamplifier is to he used. If the time integral of the signal voltageduring the signal period is equal to or greater than 2x10 B AN volts(where A is the area of the magnetic circuit in square centimeters. B isin gauss and N the number of turns), then full output is obtained fromthe amplifier. If, on the other hand, the time integral of the signalvoltage is less than 2 10- B AN volts, an output proportionately smallerthan the full output will be obtained. This elTect may be used to make alower power amplifier without decreasing the volume of mag neticmaterial present. Therefore, it is not necessary, and indeed may not bedesirable, that the amplifier opcrate with the full excursion betweenplus B and minus B as stated hereinabove.

FIGURE 6 shows some typical shapes of power pulses which might be used.FIGURE 60: shows a half sine wave; FIGURE 6b shows a triangular wave;FIGURE 60 shows a Gaussian curve; and FIGURE 6d shows a fiat-top pulsewith unequal rise time and fall time. The main considerations indetermining the shape of the power pulse are the eflcct of its shape onthe sneak pulse and output pulse, and the back voltage applied to thediode in series with the load resistance at the time that the powerpulse returns to zero. Usually, with the materials used, the greatestchange of flux between B and B occurs near B Therefore, if the powerpulse is made to travel slowly over this region, the sneak pulse wouldbe of lower amplitude during the lower rise; the output would also besmaller, though. If a power pulse as shown in FIGURE 60 is used, theoutput and sneak pulse will be as illustrated in curves Y and X, FIGURE7a, respectively. If the waveform as shown in FIGURE 6d is used, theoutput and sneak pulse will be as shown in curves Y and X, FIGURE 7b,respectively,

One of the important problems connected with these amplifiers is U18method of preventing power pulses from delivering energy to the signalinput winding and the method of preventing the signal winding fromdelivering energy to the output winding. Several methods or combinationsof methods can be used. One simple case occurs when the power winding isconnected to a high impedance source. In this case, the high impedanceitself prevents energy transfer from the signal to the power winding.Various combinations of diodes and blocking voltages can also be used onboth signal and power windings.

FIGURE 8 is an example of how diodes and blocking pulses can be used toisolate the power Winding from the input or the input from the powerwinding, whenever a constant current source is used for the inputwinding. (In the case of coil I (the power winding), the application ofa constant current source may be regarded as a rule.) The portion ofcore C containing the input winding as in FIGURE 2 is redrawn in FIG-URE 8. A similar arrangement may be used for the power circuit, but thediode corresponding to diode P would not be necessary in such a case,provided that the point corresponding to point S is connected to adevice which prevents any back flow of current. The waveforms applied inone method of using this principle are shown in FIGURE 8a. The pulseapplied to the power winding is shown. At the same time, a positivepulse is applied to point A from a blocking source. This cuts off thediode Q in series with A and prevents flow of current which, as a resultof transformer action, would try to fiow as shown by the dotted arrow.The blocking pulse has the same or greater duration as the power pulseand sufiicient amplitude to prevent the flow of current. At some latertime, as previously described, a signal pulse is applied to point A.FIGURE 8b shows an alternate method for accomplishing this result. Herethe blocking pulse is applied to the point A and the signal to point AIn this case, the polarities of both the blocking pulse and the signalare negative,

Another method for accomplishing the same thing is shown in FIGURE 80.The power pulse is the same as previously described. Now, however, awaveform as shown in the second line is applied to terminal S. Thiswaveform is called the block and signal supply because it is of thecorrect polarity to block during the power pulse period, and it cansupply power to the signal winding in the event that a waveform, asshown in the last line, appears at point A. Point A would be grounded inthis case, and diode P may be eliminated.

FIGURE 9 shows a method of isolating the power pulse from the input whenusing a constant voltage source. Here again only coil III and part ofcore C, as in FIGURE 2, are shown. A power pulse is applied as shown inFIGURE 9a. During the period of the power pulse, a blocking voltage froma low impedance source is applied at point A. This acts to cut oil thediode P in series with terminal A and prevents current from flowing inthe direction of the dotted arrow. This is the direction in which thepower pulse would tend to make the current flow. A signal pulse as shownin the bottom waveform of FIGURE 9a is selectively applied at point A.

FIGURE 10 shows both DC. power sources and blocking pulses which can beused on both power and signal windings in an amplifier. A power pulse isapplied as shown at point B and the constant current from S whichnormally would fiow to B, is made to flow through coil I. Similarly, ablocking voltage is applied at point A During the signal period, apositive signal pulse is applied to terminal A and the current from S,which normally would flow through A, is made to flow through coil III. Apositive blocking voltage is applied at point B Note that if a signalpulse does not occur, the block is applied anyhow so that the signalsource does not have to supply power required to block. The applicationof the block in no way harms the operation of the amplifier.

In the preliminary description of the operation of the amplifier, theoutput winding was shown as a separate winding 11 of FIGURE 2 and otherfigures. However, it is not necessary that this be so. The output may beconnected as shown in FIGURE 11, Le, across the power winding I with thediode D in series with the load R The input and output waveforms are thesame as shown before. The previously discussed principles, for example,those of FIGURE 10, can be still applied to this circuit. A block suchas applied at B FIGURE 10, can also be applied at B FIGURE 11. A powerpulse can be applied at B, FIGURE ll, or if terminal B is eliminated, itcan be applied at point S as described in connection with FIGURE 80. Thepower pulse applied at B may also serve as a blocking pulse if it isallowed to go negative, as shown in FIGURE 110. In this case point Bwould be grounded.

A magnetic amplifier may be constructed having only one coil on a coreof ferromagnetic material. An example of a single coil magneticamplifier is shown in FIGURE 12. This amplifier has a constant currentapplied via resistor R During the power period, when the power input hasa positive pulse applied thereto, diode D cuts oil and current flowsthrough resistor R the amplifier coil and diode D in series and throughdiode D and the load resistor R Assuming that there has been no signalinput, the core will be at plus B flux density, when the power pulsearrives, and will travel from plus B to plus 13 and there will be only asmall voltage across R and only a sneak output pulse will result.

During the signal input period, a negative pulse is applied to the powerinput. Diode D will connect, and point A will be at the potential of thenegative pulse applied to the power input. Diodes D and D willdisconnect, and no current will flow through the amplifier coil. If asignal input is applied at this time through capacitor F, diode D willconnect, and a current will flow through the amplifier coil in thereverse direction, driving the core from plus B flux density to minus Bflux density. Then, during the next power pulse, the core will travelfrom minus B to plus B and a large output will result.

A voltage gain may be obtained from this amplifier by connecting diode Dto point B instead of point X as shown. In this case it will requireless voltage (although more current) to reset the amplifier from plus Bto minus BR- In the magnetic amplifiers previously described, it issometimes desirable to obtain a steady output, when pulses are appliedto the input. This can be done by utilizing a rectifier or suitablefilter circuit or integrating circuit on the output.

FIGURES l3 and 13a illustrate one such circuit for obtaining a steady orstretched output. Referring now to FIGURE 13 there is shown a capacitorF connected across a load resistor R of a magnetic amplifier to form anintegrating network. This composite load (R -l-F) is in turn connectedin parallel with the output winding II of the magnetic amplifier. FIGURE13 illustrates that this integrating circuit could be connected acrossthe load winding II of any of the previously described magneticamplifiers, and is particularly applicable to the amplifiers shown inFlGURES 2 and 10.

The operation of the circuit may be best understood by examining FIGURE13a which shows a three winding magnetic amplifier A of the type alreadydescribed in connection with FIGURES 2 and It). Amplifier A comprisesthree windings I, II and III coupled to a magnetic core C. Windings Iand III receive in the times allotted therefor (as previously described)the power and signal pulses respectively. Power pulses cause the core tobe driven to plus flux saturation, plus B and signal pulses cause thecore to be driven to minus flux saturation, minus B When the power pulsedrives the core from minus B to plus B a change in flux will begenerated which induces an output voltage across output winding II. Thisoutput voltage in turn is transmitted to the integrating circuitcomprising resistor R and capacitor F. Although FIGURE 13a illustratesthe power winding I and the signal winding III being driven fromconstant current sources of the type shown and described in connectionwith FIGURE 4 it will be appreciated that this magnetic amplifier andthe integrating circuit comprising resistor R and capacitor F wouldoperate equally as well if the magnetic amplifier were driven by voltagesources (see FIG. 5).

In operation magnetic amplifier A produces an output pulse acrosswinding II after a signal has been applied to winding III. The outputpulse developed to some degree depends on the quality of the appliedinput signal of winding III. If the time integral of the signal is lessthan 2 l0- B AN volts then a full output will not be developed inresponse to the voltage applied to winding I. However, if the timeintegral of the applied input signal is equal or greater than therequisite volt second to entirely flip the core (i.e. drive the core tominus flux saturation, minus B then when the voltage is applied towinding I a full standard output pulse will be developed across outputwinding II as the core experiences a traversal of its hysteresis loop.This output pulse will of course operate on the composite load (i.e. theintegrating circuit comprising resistor R and capacitor F) and a steadyor stretched output from amplifier A will be obtained. If it is desiredto reduce the steady output to Zero, the input pulses to the amplifierare removed. It may take several pulse periods for the charge to leakoff capacitor F. If a faster decay is desired, a clamp pulse could beapplied to the output to reduce the output rapidly to zero.

Another circuit which may be used to obtain a stretched output is shownin FIGURES l4 and 14a. Referring to FIGURE 14 there is shown a delayline D coupled in parallel to the output winding II of a magneticamplifier. Again this figure illustrates that the pulse stretching ap- 9paratus could be coupled across the load winding 11 of any of themagnetic amplifiers previously described.

Referring now to FIGURE 14a there is shown a three winding magneticamplifier A of the type just described connected at its output windingII via a plurality of diodes D D and D to the taps of a lumped parameterdelay line D which is terminated by its characteristic impedance R Thedelay line makes use of the propagation time from the various points onthe delay line to the output to increase the length of the pulse. In anamplifier which operates on a 50-50 duty cycle, i.e., one in which thesignal period and power period are of equal length, only two diodeswould be necessary. The delay time between the two diodes would be equalto the length of either the signal or power periods. By the time themain output pulse injected at the output end of the delay line wouldhave died down, the pulse from the diode down the transmission line,which is delayed by a time equal to the power pulse period, will havearrived at the output, and it will last for a period equal to the signalperiod. Therefore, a steady output will be obtained when pulses areapplied to the delay line. This type of circuit has the advantage of amuch more rapid fall time than the capacitor circuit shown in FIGURE 13and, in general, no reset pulse will be required with this type ofcircuit.

Of course, where the pulse periods are not the same, for example, wherethe power period is shorter than the signal period, the same type ofcircuit could be used. However, it would be necessary to use more thantwo diodes. In the circuit of FIGURE 140, three diodes are shown. Thiscould be used for any signal period length up to the point where thesignal period is twice the power period. it is evident how thisprinciple can be extended to include duty cycles of any ratio.

While specific embodiments have been described in detail to illustratethe principles of the invention, many modifications and variations forapplying such principles in other arrangements, but which will notdepart materially from the spirit of the invention, will be apparent tothose skilled in the art.

What is claimed is:

1. A magnetic device comprising a magnetic core, a biasing coil coupledto said core, an input coil coupled to said core, means for applyingdirect current to said biasing coil to produce magnetic flux in onedirection, means for applying a signal to said input coil to producemagnetic flux in an opposing direction, an output coil coupled to saidcore, and an integrating circuit coupled to said output coil.

2. A magnetic device comprising a magnetic core, a biasing coil coupledto said core, an input coil coupled to said core, means for applyingdirect current to said biasing coil to produce magnetic flux in onedirection, means for applying a pulse waveform to said input coil toproduce magnetic flux in an opposing direction, an

output coil coupled to said core, and an integrating circuit coupled tosaid output coil, said integrating circuit having a discharge timelonger than the duration of the pulses in said waveform.

3. In a parallel magnetic amplifier comprising a core of ferromagneticmaterial, a winding coupled to said core, means coupled to said core fordriving said ferromagnetic material to a first or second state ofmagnetic remanence and for inducing .a predetermined output across saidwinding when said ferromagnetic material is driven from said first stateto said second state, a load circuit coupled in parallel to said windingwherein said load circuit includes a resistor and capacitor connected inparallel, and a unilateral conductor interposed between said winding andsaid load circuit.

4. In a parallel magnetic amplifier comprising a core of ferromagneticmaterial, a winding coupled to said core, means coupled to said core fordriving said ferromagnetic material to a first or second state ofmagnetic remanence and for inducing a predetermined output across saidwinding when said ferromagnetic material is driven from said first stateto said second state, a load circuit coupled in parallel to saidwinding, said load circuit including a plurality of unilateralconductors, a delay line and an impedance element wherein saidunilateral conductors are connected between one end of said winding anddifferent points on said delay line and said impedance is connected tothe end of said delay line.

5. In combination, a core of ferromagnetic material, a first, a secondand a third electric winding associated with said core, a source ofpower pulses connected to said first winding, a load circuit coupledacross said second winding, said load circuit comprising an impedanceand a capacitor connected in parallel, a unilateral conductor connectedin series between said load circuit and said second winding and a sourceof signal pulses connected to said third winding.

6. In combination, a core of ferromagnetic material, a first, a secondand a third electric winding associated with said core, a source ofpower pulses connected to said first winding, a source of signal pulsesconnected to said third winding, and a load circuit coupled across saidsecond winding, said load circuit comprising a plurality of unilateralconductors, a delay line and an impedance element wherein saidunilateral conductors are connected between one end of said secondwinding and dilferent points on said delay line and said impedance isconnected to the end of said delay line.

References Cited in the file of this patent UNITED STATES PATENTS2,375,609 Ziihlke May 8, 1945 2,652,501 Wilson Sept. 15, 1953 2,654,080Browne Sept. 29, 1953 2,673,337 Avery Mar. 23, 1954

2. A MAGNETIC DEVICE COMPRISING A MAGNETIC CORE, A BIASING COIL COUPLEDTO SAID CORE, AN INPUT COIL COUPLED TO SAID CORE, MEANS FOR APPLYINGDIRECT CURRENT TO SAID BIASING COIL TO PRODUCE MAGNETIC FLUX IN ONEDIRECTION, MEANS FOR APPLYING A PULSE WAVEFORM TO SAID INPUT COIL TOPRODUCE MAGNETIC FLUX IN AN OPPOSING DIRECTION, AN OUTPUT COIL COUPLEDTO SAID CORE, AND AN INTEGRATING CIRCUIT COUPLED TO SAID OUTPUT COIL,SAID INTEGRATING CIRCUIT HAVING A DISCHARGE TIME LONGER THAN THEDURATION OF THE PULSES IN SAID WAVEFORM,